The present invention relates to reproduction apparatus having copy-collating and duplexing capabilities. More specifically, the invention relates to copiers having collating document feeders and copy duplexing sections which are coordinated in operation to produce collated duplex copies from duplex and simplex originals.
The art of document handling is well developed for generating simplex copies from simplex originals. Numerous and rather sophisticated features exist, including, for example, document feeding in a sequence which automatically collates the final copies without a sorter. An especially advantageous collating document feeder is disclosed in commonly assigned copending U.S. patent application, Ser. No. 647,683, entitled Recirculating Sheet Feeder, filed on Jan. 8, 1976, in the name of Matthew Russell, such application being a continuation of application Ser. No. 523,610 filed Nov. 13, 1974, now U.S. Pat. No. 4,169,674, issued on Oct. 2, 1979.
The art of copy duplexing also is well developed for generating duplex copies from duplex originals. Examples include to so-called "single pass" approach, which establishes copy images in sequence on alternate faces of a copy support, and "double pass" approach, which uses an intermediate hopper to collect copy sheets after they receive images on one face and then refeeds the collected sheets to receive images on the alternate face. Single pass approaches are disclosed in U.S. Pat. Nos. 3,672,765, 3,869,202, and 3,947,270. Double pass approaches are disclosed in the February 1976 issue of Research Disclosure, Vol. 142, No. 14237 at page 38 (published by Industrial Opportunities Ltd., Homewell Havant, Hampshire, P09 1EF, United Kingdom), and in U.S. Pat. No. 3,719,266.
More recently, there have been attempts to combine the arts of copy collating and duplexing in convenience copiers without sorters. U.S. Pat. No. 3,630,607, is exemplary in its disclosure of copying apparatus including a collating document feeder and a copy-duplexing section. The feeder circulates original document sheets a plurality of times to en exposure position in a manner suitable for collating the final copies. Both faces of a duplex original can be copied by manually turning the document over after all of the sheets are copied on one face. The duplexing section includes a top-feeding intermediate hopper and a "double pass" paper path for inverting the copy supports and presenting both faces of the supports for receiving copy images.
Prior art approaches such as those referred to above, which have both collating and duplexing capability, are not entirely automatic in operation. Although it might appear on first impression that automation could be accomplished without too much difficulty, undesirable problems remain with the obvious solutions. In prior double pass approaches, for example, the first completed copy cannot be delivered until all of the copies receive images on their first face. Only then does any copy receive an image on its second face.
Other particularly perplexing problems are encountered when additional features are contemplated in fully automated apparatus. Prior art methods of producing duplex copies from simplex originals, for example, may require separation of the original into odd-page and even-page sets, so the odd pages can be copied on ascending order and the even pages in descending order.
The cross-referenced patent applications cite additional prior art approaches and offer solutions to many of the problems. The present invention is directed to these same problems, but offers a unique solution possessing its own further advantages which are not available from the teachings of the prior art.